Who was really behind the Lockerbie bombing?

As the world marks the 25th Lockerbie attack anniversary, we ask why there is no clarity on who was the perpetrator.

Commemorations have been held in the US, UK and Scotland to mark 25 years since Pan Am flight 103 crashed over Lockerbie, Scotland, killing 270 people. But after all these years, there are still questions about who was responsible for one the most infamous attacks in modern times.

If you are looking [for evidence] in the wrong place then you are not going to find the right people. I am afraid that the enquiry spent rather a long time looking in the wrong place.

Morag Kerr, the author of 'Adequately Explained by Stupidity? Lockerbie, Luggage and Lies'

The UK, US and Libyan governments have promised to work together to reveal the full facts of the bombing.

On December 21, 1988, the quaint Scottish town of Lockerbie was about to become the scene of one of the world's most infamous attacks.

The airliner had just left London's Heathrow airport – on its way to New York.

Less than half an hour after takeoff a bomb detonated, triggering an explosion and killing all 259 people on board. Most of the passengers were American while 11 others on the ground were also killed.

Three years later, a joint indictment by the US and Scotland implicated two Libyans for the bombing.

One of them was Abdel Baset al-Megrahi, who was accused of 270 counts of murder, conspiracy to murder and breach of aviation security.

In April 1999, the suspects, including al-Megrahi, surrendered and were flown from the Libyan capital, to the Netherlands, where the case was heard.

Over the last 25 years, a lot of the focus has been on the perpetrators of the bombing … What about the victims' families?

Jim Swire, who lost his daughter in the bombing

When the trial began in 2000, al-Megrahi pleaded not guilty but he was later convicted. In 2002, he re-launched an appeal which was unsuccessful and al-Megrahi started his life sentence behind bars in a Scottish prison.

The Libyan authorities formally accepted responsibility for the attack, and even paid out $2.7bn in compensation to the relatives of those killed. That move prompted the United Nations to lift its sanctions.

Six years into his prison sentence, it was revealed that al-Megrahi suffered from advanced prostate cancer. He was given just a short time to live, and on those grounds, a Scottish judge decided to free him.

He arrived home to Libya to a hero's welcome, which upset people around the world and triggered international condemnation.

The last interview al-Megrahi gave, was while he was on his death bed in 2011.

When we did the investigation, we collected all the evidence that was available … and when it was all said and done the evidence we collected pointed to Megrahi, Fhimah and Libya.

Richard Marquise, head of FBI's taskforce on the Lockerbie investigation

He spoke about the man whose testimony helped convict him - Tony Gauci, a shopkeeper in Malta - who said Megrahi bought clothes in his store that were found wrapped around the bomb on the plane.

"If I have a chance to see him [Gauci] I am forgiving him. I would tell him that never in my entire life have I been in his shop. I never bought any clothing from him. And ... I would tell him ... that he dealt with me very wrongly," Megrahi said in his last interview.

Last year, the man known as the Lockerbie bomber died. Al-Megrahi has always said he is innocent, and his family, to this day, say they want an appeal against his sentence and demand the truth be revealed.

As the world remembers Lockerbie 25 years on, divisions remain between those who believe he was really guilty of the crime and those who do not.

So do we know who was really behind the bombing? Have investigators failed to nail the perpetrator? Was al-Megrahi a scapegoat? And how strong were the evidences that convicted al-Megrahi?

To discuss this, Inside Story presenter Folly Bah Thibault is joined by guests: Jim Swire, who lost his daughter in the bombing and led a high-profile campaign for justice on behalf of the UK victims' relatives; Richard Marquise, then head of FBI's task force on the Lockerbie investigation; Morag Kerr, the author of Adequately Explained by Stupidity? Lockerbie, Luggage and Lies; and Anas el-Gomati, the director general of Libya's first public policy think-tank Sadeq Institute.

"In 1988-1990 there was talk of Iranians being involved, Syrian's being involved, Palestinian's being involved .... Gaddafi's ego is central to the way in which this story played out .... Because of Gaddafi's need to become relevant he was very happy at the time to take credit for this ... In that sense the culpability of the international community here is quite possibly the darkest of the components of this kind of story ... There was a lot of political pressure."

Anas el-Gomati, the director general of Libya's first public policy think-tank Sadeq Institute